HMOX1 and liver cancer: After adjusting for age, gender, cigarette smoking, and arsenic exposure, the HO-1 genotype was found to be significantly associated with liver cancer risk among the study subjects based on an additive model (a trend test, HR = 2.11, 95% CI 1.16–3.87) or a recessive model (HR= 3.07, 95% CI 1.35–6.95) (Table 3).